Control valve assembly

ABSTRACT

An assembly for use in a system for heating water comprises a heat exchanger for heating cold water to produce overheated hot water and a blending chamber in which the overheated hot water is mixed with cold water to produce blended hot water. An inlet valve controls the flow of cold water to the heat exchanger. A bypass valve controls the flow of cold water into the blending chamber. A flow restrictor restricts the flow of cold water from the bypass valve into the blending chamber when the demand for blended hot water increases above a predetermined amount.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates to a hot water heating system for blendingcold water with overheated hot water to form a stream of hot waterhaving a predetermined temperature. In particular, the present inventionrelates to a control valve assembly that maintains the stream of hotwater at a nearly constant temperature over a wide range of flow ratesof the hot water.

In many hot water heating systems such as institutional systems, coldwater is heated by steam in a heat exchanger. For practical reasons, theoutput flow from the heat exchanger is overheated and is much too hot tobe used at a hot water tap. Accordingly, the overheated water is blendedwith cold water in a blending chamber until a mixture having temperaturesuitable for the hot water tap is obtained.

Difficulties have been encountered in producing a control valve assemblythat can maintain the temperature of the hot water substantiallyconstant over a wide range of flow demand. To maintain the temperatureof the hot water leaving the blending chamber substantially constantover the range of flow rates, the ratio between the overheated waterarriving in the blending chamber and the cold water arriving in theblending chamber must be varied. There are two reasons for this. First,the pressure drop associated with the heat exchanger changes as the rateof flow through the heat exchanger changes. Second, the overheated watertemperature tends to fall with increase of flow through the heatexchanger.

A substantial breakthrough in control valve assemblies for hot waterheating systems described above has been achieved in a valve controlassembly disclosed in U.S. Pat. No. 4,219,044 issued to the presentinventor and incorporated herewith by reference.

In the control valve assembly disclosed in U.S. Pat. No. 4,219,044, theflow of cold water into the valve assembly is split. A portion of itflows through an inlet valve into the heat exchanger, and a portion ofit flows through a by pass valve into the blending chamber. The ratio ofthe cold water flow into the heat exchanger and the cold water flow intothe blending chamber is regulated by a controller. The controllercomprises a diaphragm that actuates a valve stem connected with theinlet and bypass valves.

Two hot water temperature adjustments are provided to assure that thetemperature of the hot water is very near constant over a wide range ofdemand. A first or low-flow temperature adjustment is made when thedemand for blended hot water is small, about 10% of capacity. The amountof cold water admitted through the bypass valve into the blendingchamber is adjusted by moving a bypass valve seat toward or away fromthe bypass valve member until the desired blended hot water temperatureis achieved. The second or high flow temperature adjustment is made whenthe flow is about 50% of capacity.

While performing quite satisfactory at most flow rates, the controlvalve assembly of U.S. Pat. No. 4,219,044 experiences some difficultiesin maintaining the desired blended water temperature at high flow rates.At high flow rates, the temperature of the overheated water that entersthe blending chamber from the heat exchanger falls. This decrease inoverheated water temperature results from increased flow rates throughthe heat exchanger. Accordingly, less cold water for blending isrequired at the high flow rates, while at lower flow rates an increasingamount of cold water for blending is required.

To provide for less cold water for blending at the high flow rates, aflow restrictor controls flow of the cold water into the blendingchamber. The flow restrictor moves to restrict the flow of cold waterinto the blending chamber at the high flow rates so that less cold waterenters the blending chamber.

According to the invention, the control valve assembly comprises aninlet valve and a bypass valve. A diaphragm controller which is actuatedby the difference in the fluid pressure at the inlet and the outlet ofthe control valve assembly controls the positions of the inlet andbypass valves in accordance with the required flow rate of the hotwater. A stem fixedly connected with the diaphragm of the diaphragmcontroller mounts the inlet and bypass valve. The inlet valve includesan inlet valve member and a valve seat with which the inlet valve membercooperates. The inlet valve member is fixedly connected to the stem. Thebypass valve includes a bypass valve member which is also connected tothe stem and a bypass valve seat. The restrictor is adjustably connectedto the stem for joint movement therewith and relatively thereto. Whenthe first, low-flow temperature adjustment is made, the amount of coldwater admitted through the bypass valve into the blending chamber isadjusted by moving the bypass valve seat toward and away from the bypassvalve member. The second or high-flow temperature is effected by movingthe restrictor along the stem.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and objects of the present inventionwill become more apparent upon a reading of the following specificationmade with reference to the accompanying drawings wherein:

FIG. 1 is a schematic view of a hot water system constructed inaccordance with the present invention;

FIG. 2 is an axial sectional view of a control valve assembly of thepresent invention;

FIG. 3 is a sectional view on an enlarged scale of a portion of thecontrol valve assembly of FIG. 2;

FIG. 4 is a sectional view similar to FIG. 2 but showing parts in adifferent position;

FIG. 5 is also a sectional view similar to FIGS. 2 and 3 but showingparts in still another position; and

FIG. 6 is a graph that characterizes the operation of the presentinvention.

DESCRIPTION OF A PREFERRED EMBODIMENT

A control valve assembly 10 constructed according to the presentinvention is designed for use in a system adapted to supply hot water ata substantially constant temperature over a wide range of flow rates.The system is particularly adapted for producing hot water for use inso-called institutional applications, locker rooms associated withathletic facilities, or anywhere else where the demand for hot watervaries widely from time to time. The system in which the valve assemblyaccording to the present invention is used is the same system that isdescribed in U.S. Pat. No. 4,219,044.

As shown in FIG. 1, hot water from a heat exchanger 14 is supplied to ahot water tap 15. The temperature of the hot water supplied to the hotwater tap 15 is regulated by the control valve assembly 10. The valveassembly 10 blends a precisely controlled amount of cold water withoverheated hot water from the heat exchanger 14. Steam supply 12provides steam for heating cold water in the heat exchanger 14.

The valve assembly 10 is shown in detail in FIG. 2. The valve assemblyincludes a cold water inlet 16, a blended water outlet 18, and two ports20 and 22 connected, respectively, with the inlet and outlet of the heatexchanger 14. An inlet valve 24 controls the flow of cold water to theheat exchanger, and a bypass valve 26 controls the flow of cold waterinto the blending chamber 28, where the cold water is blended with theoverheated hot water from the heat exchanger 14 that enters the chamber28 through the port 22.

The pressure drop between ports 20 and 22 equals the pressure dropacross the heat exchanger, which is a function of the flow ratetherethrough.

Both the inlet valve 24 and bypass valve 26 include valve members 32 and34 cooperating valve seats 36 and 38, respectively. In FIG. 2 it isshown that both valve members 32 and 34 are cylindrical. However, theshape of the valve members is not critical, and they may be of anysuitable form.

A controller 30 actuates the valves 24 and 26 in response to variationsin the demand for hot water. The controller 30 includes a diaphragm 40and upper and lower diaphragm cover members 42 and 44. The covers areconnected by bolts 46 and nuts 48. The diaphragm 40 forms a movablebarrier between an upper chamber 50 formed in the upper cover member 42and a lower chamber 52 formed in the lower cover member 44. The upperand lower cover members 42 and 44 are generally cylindrical and haveopposed coaxial cylindrical recesses that form the upper and lowerchambers 50 and 52, respectively.

The blended water pressure reaches the lower chamber 52 through acentral passage 56 of a tubular stem 58 which mounts both valves 24 and26. The stem 58 is fixedly connected with the diaphragm 40 which issupported between a diaphragm retainer disc 60 and a diaphragm supportdisc 62. The lower end of the stem 58 may, for example, be threaded, anda nut 64 fixes the stem 58 to diaphragm support disc 62 through a lockwasher 66.

A plug 68 blocks an opening 68a in the lower cover member 44. Thecontroller 30 is attached to the control valve housing 70 by bolts 72. Agasket 74 is located between the controller 30 and the control valvehousing 70.

The pressure acting on the top side of the diaphragm 40 is suppliedthrough a passage 76 which opens into the cold water inlet 16 and theupper chamber 50.

The inlet valve member 32 at the upper end thereof abuts a shoulder 58aon the stem 58 and is provided, at the lower end thereof with shoulder32a which abuts the upper end surface 60a of the diaphragm retainer disc60. The foregoing structure assures that the inlet valve member 32 isheld in a fixed axial position on the stem 58, and that the size of theopening defined by the inlet valve member 32 as it moves downward withthe stem 58 is directly proportional to the amount of movement of thestem 58.

A range spring 80 biases the inlet valve member 32 and the stem 58upward into a closed position shown in FIG. 2. The range spring 80 actsbetween a lower annular end surface 82 of the inlet valve member 32 andannular end surface 84 of a stem guide 86 that is fixed in the uppercover member 42, i.e., by threaded engagement therewith.

The bypass valve member 34 is also fixedly connected to the stem 58. Thebypass valve member 34 has an internal thread engaging an externallythreaded portion 88 on the stem 58. The bypass valve seat 38 is definedby a tubular sleeve 90 which also defines ports 92 through which thebypass cold water flows into the blending chamber 28. The port 92 has acircular cross section. The number of ports 92 may vary. In thedescribed embodiment, the sleeve 90 has four such ports. The sleeve 90also has one or a plurality of circular ports 92a which communicate theblending chamber 28 with the chamber into which stem passage 56 opens. Aseal 94 prevents leakage between the blending chamber 28 and the coldwater inlet 16.

The bypass valve member 34 defines a plurality of rectangularly shapedaxial slots 34a in the body thereof. In the preferred embodiment, thebypass valve member has four such slots. However, the number of slotsmay vary. The slots 34a serve to increase flow of cold water into theblending chamber 28 with increased demand for hot water at the tap.

A flow restrictor 96 controls the flow of the cold water into theblending chamber at high flow rates. The flow restrictor has a threadedlower end that threadably engages the threaded portion 88 on the stem 58and is adjustable relative to the stem. The restrictor 96 moves axiallywith the stem 58 to control flow of cold water through the ports 92.

A top cap 98 covers the sleeve 90 and is attached to the control valvebody 70 by bolts 100. A gasket 102 is located between the top cap 98 andthe control valve body 70.

The low-flow temperature adjustment of flow of cold water into theblending chamber is effected by means of an adjusting sleeve 104 mountedin the top cap 98. The adjusting sleeve 104 is attached at its lower endto the tubular sleeve 90 and moves therewith to thereby control theposition of the bypass valve seat 38. The adjusting sleeve 104 has atthe upper end thereof two flat surfaces adapted to be engaged by awrench for rotating the adjusting sleeve 104. When the adjusting sleeve104 is rotated, it moves axially relative to the top cap 98 and, thus,provides for axial movement of the tubular sleeve 90 to a desiredposition of the valve seat 38.

The high-flow temperature adjustment of the flow of cold water into theblending chamber 28 is effected by adjusting the restrictor 96 relativeto the stem 58. The adjustment is made by rotating the adjusting rod110. Rotation of the adjusting rod 110 causes rotation of trunion 108which has projections which cooperate with projections on the restrictor96 so that restrictor 96 rotates upon rotation of the rod 110. Becauseof the threaded engagement between the restrictor 96 and the stem 58,the restrictor moves relative to the stem 58. A bonnet 106 is providedfor covering the adjusting sleeve 104 and adjusting rod 110 and forpreventing unauthorized tampering therewith.

Lock screws 112 fix the bypass valve member 34 to the stem 58, theadjusting sleeve 104 to the sleeve 90, the top cap 98 to the adjustingsleeve 104, and the trunnion 108 to the adjusting rod 110.

The operation of the control valve assembly is described below. When thesystem is not operating, the inlet valve 24 is completely closed. Thebypass 26 valve is slightly open to provide cold water for blending withhot water leakage so that there is no flow of overheated hot water whenthe tap 15 opens.

Upon opening of the tap 15, the diaphragm controller 30 opens the valves24 and 26 in response to the reduction in pressure in the blendingchamber 28. This reduction in pressure is communicated to the lowerchamber 52 of the controller 30 through the ports 92a and the passage 56in the tubular stem 58. The pressure differences across the diaphragm 40causes the diaphragm to move downward. The stem 58 fixedly connected tothe diaphragm 40 also moves downwardly and open the valves 24 and 26 sothat the cold water can flow through the inlet valve 24 into the heatexchanger and through the bypass valve 26 into the blending chamber 28.As both valves are affixed to the stem, they move equal incrementalamounts. The flow area provided by the bypass valve 26 is characterizedso that at low flow rates the proper ratio of the flow of cold waterthrough the bypass valve 26 into the blending chamber and the flow ofcold water to the heat exchanger through the valve 24 is achieved, andthe preset discharge temperature remains substantially constantregardless of the total flow. Both flows increase with opening of thefaucet 15 in this range.

FIG. 4 shows the positions of the inlet and bypass valves 24 and 26 andthe restrictor 96 when the demand for the blended hot water is low. Thelow end of the restrictor 96 only slightly obstruct the passage of thecold water through the ports 92 into the blending chamber 28. In thisposition, the restrictor 96 does not affect the amount of cold waterflow into the blending chamber. This is because the cross sectional areaof ports 92 is greater than the cross sectional area of the passagebetween the bypass valve member 34 and seat 38, and it is this passagethat determines the cold water flow into the blending chamber 28 atrelatively low flow rates.

As the demand for hot water increases, the pressure in the blendingchamber 28 is further reduced. The increased pressure difference acrossthe diaphragm 40 causes the diaphragm to move further downward. The stem58 also moves further downward increasing cross section flow area ofvalves 24 and 26, and more cold water flows into the heat exchanger 14and the blending chamber 28. The restrictor 96 also moves furtherdownward, and, at predetermined position of the stem 58, whichcorresponds to a rather high flow rate, blocks the ports 92 such thatthe open cross sectional area of ports 92 will be less than the crosssectional area of the passage between the bypass valve member 34 and thevalve seat 38. Accordingly, the flow of cold water into the blendingchamber 28 will be restricted, and less cold water will flow into theblending chamber. FIG. 5 shows the position of the inlet and bypassvalves 24 and 26 and the restrictor 96 when the demand for blended hotwater is high.

As previously noted, two adjustments are made to the control valveassembly 10 to assure that a constant preset discharge temperature ismaintained. Initially, at low flow rates, both valves 24 and 26 arecooperating. Then, at intermediate flow rates, the flow area of thebypass valve 26 is increased, while the flow restrictor 96 decreases theflow area of the ports 92. Finally, the bypass flow decreases to zero atcritical high flow rates when the overheated water temperature reachesthe set point temperature.

The first adjustment is made at low flow conditions when the demand forhot water at the tap is small, about 10% of the maximum flow rate, andthe flow rate through the heat exchanger is small, that is, when theinlet valve 24 and the bypass valve 26 are open a small amount as shownin FIG. 4. This adjustment is effected by moving the bypass valve seat38 toward and away from the bypass valve member 34.

To move the bypass valve seat 38, the cap 106 is removed, and theadjusting sleeve 104 is rotated by a wrench to thereby move axially thetubular member 90 that mounts the bypass valve seat 38. First adjustmentis effected to create a pressure drop against the bypass water flow,which pressure drop forces the cold water through the heat exchanger.

The second adjustment is made when the demand for blended hot water islarge and constitute at least 50% of the maximum flow rate. Thisadjustment is made by positioning the flow restrictor 96 with respect tothe port 92. By rotating the adjusting rod 110, movement is transmittedto the flow restrictor 96 and, the flow restrictor is moved somewhatdownward reducing the area of the port 92. With an increased demand forhot water above a predetermined amount less cold water flows through theport 92 into the blending chamber. That corresponds to the reduceddemand for cold water at high flow rates. Operation of the system willbe more clearly understood from the graphs shown in FIG. 6.

The first graph shows that the temperature of the overheated hot waterfrom the heat exchanger drops rather sharply at the increase in the flowrate up to 25% of the maximum flow rate and then begins to decline moregradually until it remains almost constant at flow rates close to themaximum flow rate.

The second graph shows that the flow rate of the hot water increases atalmost constant ratio with respect to the demand. Not so for theoverheated hot water from the heat exchanger.

The third graph shows the flow rate of the overheated hot water at flowrates up to 25% of the maximum flow rate increases proportionally to thedemand but at a lesser ratio than the flow rate of the hot water fromthe system. This follows from the fact that the temperature of theoverheated hot water is rather high. From 25% of the maximum flow rateto approximately 75% of the maximum flow rate, the flow rate of theoverheated hot water increases almost at constant ratio with respect tothe demand. Then, the ratio of flow of the overheated hot waterincreases again. This is due to the declining flow rate of the bypassedcold water.

The fourth graph shows changes in the flow rate of bypassed cold waterduring operation of the control valve assembly. After a first adjustmentis made, at 10% of the maximum flow rate, the inlet valve and the bypassvalve moves open in phase relationship providing for proportionalincrease in cold water flow into the blending chamber, as shown by thefirst portion of the graph. This phase movement takes place up toapproximately 25% flow rate of the maximum flow rate. The flowrestrictor during this phase of operation does not yet influence theflow of cold water into the blending chamber.

The second portion of the fourth graph shows that the need for coldwater for blending remains almost constant at the range of flow ratesfrom 25% to approximately 60% of the maximum flow rate. The bypass valveand the restrictor acting in series provide for desired, almost constantflow of cold water into the blending chamber.

At flow rates from 60% of the maximum flow rate and up to the maximumflow rate, there is a declining need for cold bypassed water, asrepresented by the third portion of the graph. To provide for reducedflow of the bypass cold water into the blending chamber, a secondadjustment is made. The second adjustment is effected by properadjusting of the restrictor to the bypass valve member, as discussedabove.

While a particular embodiment of the invention has been shown anddescribed, various modifications thereto will be readily apparent tothose skilled in the art and, therefore, it is not intended that theinvention be limited to the disclosed embodiment or details thereof, anddepartures may be made therefrom within the spirit and scope of thepresent invention as defined in the appended claims.

Having described a specific preferred embodiment of the invention, thefollowing is claimed:
 1. An assembly comprising:a heat exchanger forheating cold water to produce overheated hot water, a blending chamberin which the overheated hot water from said heat exchanger is blendedwith cold water to produce blended hot water suitable for use at a hotwater tap, a first valve means for controlling flow of cold water intosaid heat exchanger according to the demand for hot water at the hotwater tap, a second valve means for controlling flow of cold water intosaid blending chamber, and a flow restrictor means for restricting flowof cold water from said second valve into said blending chamber when thedemand for blended hot water is increased above a predetermined amount.2. An assembly as set forth in claim 1 further comprising actuator meansfor controlling the operation of said first and second valve means inaccordance with the demand for hot water.
 3. An assembly as set forth inclaim 2, wherein said actuator means comprises a diaphragm controllerincluding an axially movable stem and diaphragm means fixedly connectedwith said stem for axially moving the same in response to a varyingdemand for blended hot water, said first valve means and said secondvalve means comprising first and second valve members, respectively,said first and second valve members being fixedly mounted on said stemfor axial movement therewith.
 4. An assembly as set forth in claim 1,further including first adjusting means for adjusting said second valvemeans at a predetermined low flow rate of hot water and second adjustingmeans for adjusting said restrictor means at a predetermined high flowrates with respect to said second valve means.
 5. An assembly as setforth in claim 4, wherein said first and second valve means and saidflow restrictor means are located in a common housing means, and each ofsaid first and second adjusting means includes means located outsidesaid housing for facilitating operation of the same.
 6. An assemblycomprising a housing, said housing having a first inlet for receiving anincoming flow of cold water from a cold water source, a first outlet forsupplying cold water to a heat exchanger, a second inlet for receivingoverheated hot water from said heat exchanger, a blending chamber inwhich overheated hot water is blended with cold water to produce hotwater, and a second outlet for supplying blended hot water to a point ofuse, first valve means for controlling the flow of cold water from saidfirst inlet to said first outlet, second valve means for controlling theflow of cold water into said blending chamber, control means responsiveto changes in the demand for blended hot water for varying the flow ofcold water through said first and second valve means and for restrictingflow of cold water into said blending chamber when the demand for hotwater increases above a predetermined amount.
 7. An assembly as setforth in claim 6 wherein said control means includes actuator means forcontrolling operation of said first and second valve means and a flowrestrictor for restricting flow from said second valve means into saidblending chamber when the demand for blended hot water increases abovepredetermined amount.
 8. An assembly as set forth in claim 6, whereinsaid first valve means includes a first valve member and a first valveseat, said second valve means including a second valve member and asecond valve seat, said actuator means including an axially movable stemand diaphragm means connected with said stem for moving said stem in oneaxial direction in response to increasing demand for blended hot waterfrom said second outlet and in the opposite direction in response todecreasing demand for hot water, said second valve seat being defined bya cylindrical tubular member, said tubular member also defining portmeans through which cold water from said first inlet flows into saidblending chamber, said first and second valve members being fixedlyconnected with said stem for joint axial movement therewith, said stemhaving an upper end portion projecting inside said tubular member, andsaid flow restrictor being located inside said tubular member andadjustably affixed on said stem.
 9. An assembly as set forth in claim 7,wherein said flow restrictor means further comprises a trunnionconnected with said restrictor at upper end of said restrictor, saidtrunnion being connected with an adjusting rod, rotation of saidadjusting rod providing for axial and rotatable movement of saidrestrictor relative to said upper end portion of said stem.
 10. Anassembly as set forth in claim 8, wherein said rod projects outside saidcontrol valve assembly housing.